Nanoparticle ink composition, light-emitting device, and method of manufacturing the light-emitting device

This application claims priority from and the benefit of Korean Patent Application No. 10-2020-0186765, filed on Dec. 29, 2020, which is hereby incorporated by reference for all purposes as if fully set forth herein.

Embodiments of the invention relate generally to a nanoparticle ink composition, and more particularly, to a light-emitting device, and a method of manufacturing the light-emitting device.

Light-emitting devices convert electrical energy into light energy. Examples of such light-emitting devices include organic light-emitting devices in which a light-emitting material is an organic material, and quantum dot light-emitting devices in which the light-emitting material is a quantum dot.

A light-emitting device may have a structure in which a first electrode, a hole transport region, an emission layer, an electron transport region, and a second electrode are sequentially formed. Holes provided from the first electrode may move toward the emission layer through the hole transport region, and electrons provided from the second electrode may move toward the emission layer through the electron transport region. The holes and the electrons recombine in the emission layer to produce excitons. These excitons transition from an excited state to a ground state to thereby generate light.

The above information disclosed in this Background section is only for understanding of the background of the inventive concepts, and, therefore, it may contain information that does not constitute prior art.

Compositions made, light-emitting devices constructed, and/or methods according to illustrative implementations of the invention are capable of providing one or more embodiments of a nanoparticle ink composition, a light-emitting device, and a method of manufacturing the light-emitting device.

Additional features of the inventive concepts will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the inventive concepts.

According to one aspect of the invention, a nanoparticle ink composition includes: a solvent; and one or more inorganic nanoparticles substantially dispersed in the solvent, wherein the inorganic nanoparticles include one or more quantum dots or a metal oxide having a diameter of about 20 nm or less, and the nanoparticle ink composition has an Ohnesorge number of about 0.1 to about 0.2.

A light-emitting device may include: a first electrode; a second electrode facing the first electrode; and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, and at least one of layers included in the interlayer is made from the nanoparticle ink composition as described above.

A method of manufacturing a light-emitting device, the light-emitting device include: a first electrode; a second electrode facing the first electrode; and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, a hole-transporting region between the first electrode and the emission layer, and an electron-transporting region between the emission layer and the second electrode; and the method includes the steps of:

It is to be understood that both the foregoing general description and the following detailed description are illustrative and explanatory and are intended to provide further explanation of the invention as claimed.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various embodiments or implementations of the invention. As used herein “embodiments” and “implementations” are interchangeable words that are non-limiting examples of devices or methods employing one or more of the inventive concepts disclosed herein. It is apparent, however, that various embodiments may be practiced without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring various embodiments. Further, various embodiments may be different, but do not have to be exclusive. For example, specific shapes, configurations, and characteristics of an embodiment may be used or implemented in another embodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated embodiments are to be understood as providing illustrative features of varying detail of some ways in which the inventive concepts may be implemented in practice. Therefore, unless otherwise specified, the features, components, modules, layers, films, panels, regions, and/or aspects, etc. (hereinafter individually or collectively referred to as “elements”), of the various embodiments may be otherwise combined, separated, interchanged, and/or rearranged without departing from the inventive concepts.

The use of cross-hatching and/or shading in the accompanying drawings is generally provided to clarify boundaries between adjacent elements. As such, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, dimensions, proportions, commonalities between illustrated elements, and/or any other characteristic, attribute, property, etc., of the elements, unless specified. Further, in the accompanying drawings, the size and relative sizes of elements may be exaggerated for clarity and/or descriptive purposes. When an embodiment may be implemented differently, a specific process order may be performed differently from the described order. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to the described order. Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it may be directly on, connected to, or coupled to the other element or layer or intervening elements or layers may be present. When, however, an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. To this end, the term “connected” may refer to physical, electrical, and/or fluid connection, with or without intervening elements. Further, the D1-axis, the D2-axis, and the D3-axis are not limited to three axes of a rectangular coordinate system, such as the x, y, and z-axes, and may be interpreted in a broader sense. For example, the D1-axis, the D2-axis, and the D3-axis may be perpendicular to one another, or may represent different directions that are not perpendicular to one another. For the purposes of this disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be construed as X only, Y only, Z only, or any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms “first,” “second,” etc. may be used herein to describe various types of elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,” “above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), and the like, may be used herein for descriptive purposes, and, thereby, to describe one elements relationship to another element(s) as illustrated in the drawings. Spatially relative terms are intended to encompass different orientations of an apparatus in use, operation, and/or manufacture in addition to the orientation depicted in the drawings. For example, if the apparatus in the drawings is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and, as such, the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, the singular forms, “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Moreover, the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The term “consist of” used herein refers to the existence of only the corresponding component while excluding the possibility that other components are added. For example, the wording “consist of A, B and C” refers to the existence of only A, B and C. It is also noted that, as used herein, the terms “substantially,” “about,” and other similar terms, are used as terms of approximation and not as terms of degree, and, as such, are utilized to account for inherent deviations in measured, calculated, and/or provided values that would be recognized by one of ordinary skill in the art.

Various embodiments are described herein with reference to sectional and/or exploded illustrations that are schematic illustrations of idealized embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments disclosed herein should not necessarily be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. In this manner, regions illustrated in the drawings may be schematic in nature and the shapes of these regions may not reflect actual shapes of regions of a device and, as such, are not necessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is a part. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense, unless expressly so defined herein.

A nanoparticle ink composition according to one aspect includes a solvent, one or more inorganic nanoparticles dispersed in the solvent, wherein the inorganic nanoparticles are quantum dots or a metal oxide having a diameter of about 20 nanometer (nm) or less, and the nanoparticle ink composition has an Ohnesorge number of about 0.1 to about 0.2.

In this regard, the Ohnesorge number is a value consisting of the relationship between the surface tension and viscosity of an ink composition, and can be expressed by Equation 1 below.

In Equation 1, Oh is the Ohnesorge number,

Conventionally, even when the weight percent (weight % or wt %) of particles in an ink composition, the boiling point of a solvent, the surface tension, the viscosity are all considered, jetting failure sometimes occur.

Within the Ohnesorge number condition of about 0.1 to about 0.2, the nanoparticle ink composition may be properly jetted. When the nanoparticle ink composition has an Ohnesorge number of less than about 0.1 or greater than about 0.2, the nanoparticle ink composition may not be jetted. In one or more embodiments, the surface tension of the nanoparticle ink composition may be from about 20 dyne/cm to about 50 dyne/cm.

In one or more embodiments, the viscosity of the nanoparticle ink composition at a temperature of 25° C. may be from about 1 cP (centipoise) to about 12 cP. In one or more embodiments, the density of the nanoparticle ink composition may be from about 0.8 g/cmto about 2.0 g/cm. For example, the nanoparticle ink composition may consist of the solvent and the nanoparticles. In one or more embodiments, the solvent may be an alcohol-based solvent having two or more carbon atoms, an ether-based solvent, an aromatic solvent, or a combination thereof.

For example, the solvent may include an ether-based solvent or a mixture of ether-based solvents and other solvents. For example, the solvent may include a mixture of ether-based solvents and other solvents. In one or more embodiments, the solvent may have the boiling point of about 150° C. to about 350° C., about 170° C. to about 320° C., or about 200° C. to about 300° C. so that ink droplets are stably jetted to prevent ink dryness in a nozzle part of an inkjet print head.

For example, the solvent may include a cyclohexylbenzene (the boiling point of about 240° C.), 1,3-dipropoxybenzenne (the boiling point of about 251° C.), 4-methoxybenzaldehyde-dimethyl-acetal (the boiling point of about 253° C.), 4,4′-difluorodiphenylmethane (the boiling point of about 258° C.), diphenylether (the boiling point of about 259° C.), 1,2-dimethoxy-4-(1-propenyl)benzene (the boiling point of about 264° C.), 2-phenoxytoluene (the boiling point of about 265° C.), diphenylmethane (the boiling point of about 265° C.), 2-phenylpyridine (the boiling point of about 268° C.), dimethyl benzyl ether (the boiling point of about 270° C.), 3-phenoxytoluene (the boiling point of about 272° C.), 3-phenylpyridine (the boiling point of about 272° C.), 2-phenylanisole (the boiling point of about 274° C.), 2-phenoxytetrahydropuran (the boiling point of about 275° C.), 1-propyl-4-phenyl benzene (the boiling point of about 280° C.), 2-phenoxy-1,4-dimethyl benzene (the boiling point of about 280° C.), ethyl-2-naphthyl-ether (the boiling point of about 282° C.), dodecylbenzene (the boiling point of about 290° C.), 2,2,5-tri-methy diphenyl ether (the boiling point of about 290° C.), dibenzyl-ether (the boiling point of about 295° C.), 2,3,5-tri-methy diphenyl ether (the boiling point of about 295° C.), N-methyldiphenylamine (the boiling point of about 297° C.), 4-isopropylbiphenyl (the boiling point of about 298° C.), α,α-dichlorodiphenylmethane (the boiling point of about 305° C.), 4-(3-phenylpropyl)pyridine (the boiling point of about 322° C.), benzyl-benzoate (the boiling point of about 324° C.), 1,1-bis(3,4-dimethylphenyl)ethane (the boiling point of about 333° C.), diethyleneglycolbutylmethylether (DEGBME), diethyleneglycolmonomethylether (DEGME), diethyleneglycolethylmethylether (DEGEME), diethyleneglycoldibutylether (DEGDBE), propylene glycol methylether acetate (PGMEA), triethylene glycol monomethylether (TGME), diethyleneglycolmonobutyl ether (DGBE), or a combination thereof.

For example, the solvent may include a cyclohexylbenzene, a propylene glycol methyl ether acetate, a triethylene glycol monomethyl ether, a diethylene glycol monobutyl ether, or a combination thereof. In one or more embodiments, the amount of the inorganic nanoparticles may be about 10 wt % or less based on the total weight of the nanoparticle ink composition. In one or more embodiments, the amount of the inorganic nanoparticles may be less than about 10 wt % based on the total weight of the nanoparticle ink composition. For example, the amount of the inorganic nanoparticles may be from about 0.01 wt % to about 10 wt % based on the total weight of the nanoparticle ink composition. For example, the amount of the inorganic nanoparticles may be from about 0.05 wt % to about 10 wt % based on the total weight of the nanoparticle ink composition. For example, the amount of the inorganic nanoparticles may be from about 0.1 wt % to about 10 wt % based on the total weight of the nanoparticle ink composition.

A diameter of the quantum dot may be, for example, in a range of about 1 nm to about 10 nm. The quantum dot may be synthesized by a wet chemical process, a metal organic chemical vapor deposition process, a molecular beam epitaxy process, or any process similar thereto. According to the wet chemical process, a precursor material is mixed with an organic solvent to grow a quantum dot particle crystal. When the crystal grows, the organic solvent naturally acts as a dispersant coordinated on the surface of the quantum dot crystal and controls the growth of the crystal so that the growth of quantum dot particles can be controlled through a process which is more easily performed than vapor deposition methods, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), and which requires low costs.

The quantum dot may include a semiconductor compound of Groups II-VI, a semiconductor compound of Groups III-V, a semiconductor compound of Groups III-VI, a semiconductor compound of Groups I, III, and VI, a semiconductor compound of Groups IV-VI, an element or a compound of Group IV; or any combination thereof.

Examples of the semiconductor compound of Groups II-VI are a binary compound, such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, or MgS; a ternary compound, such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, or MgZnS; a quaternary compound, such as CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, or HgZnSTe; or any combination thereof.

Examples of the semiconductor compound of Groups III-V are a binary compound, such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or the like; a ternary compound, such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InAlP, InNAs, InNSb, InPAs, InPSb, or the like; a quaternary compound, such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or the like; or any combination thereof. The semiconductor compound of the Groups III-V may further include Group II elements. Examples of the semiconductor compound of Groups III-V further including Group II elements are InZnP, InGaZnP, InAlZnP, etc.

Examples of the semiconductor compound of Groups III-VI are a binary compound, such as GaS, GaSe, GaSe, GaTe, InS, InSe, InS, InSe, or InTe; a ternary compound, such as InGaS, or InGaSe; and any combination thereof. Examples of the semiconductor compound of Groups I, III, and VI are a ternary compound, such as AgInS, AgInS, CuInS, CuInS, CuGaO, AgGaO, or AgAlO; or any combination thereof.

Examples of the semiconductor compound of Groups IV-VI are a binary compound, such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or the like; a ternary compound, such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or the like; a quaternary compound, such as SnPbSSe, SnPbSeTe, SnPbSTe, or the like; or any combination thereof. The Group IV element or compound may include a single element compound, such as Si or Ge; a binary compound, such as SiC or SiGe; or any combination thereof.

Each element included in a multi-element compound such as the binary compound, ternary compound and quaternary compound, may exist in a particle with a uniform concentration or non-uniform concentration.

The quantum dot may have a single structure or a dual core-shell structure. In the case of the quantum dot having a single structure, the concentration of each element included in the corresponding quantum dot is uniform. In one or more embodiments, the material contained in the core and the material contained in the shell may be different from each other.

The shell of the quantum dot may act as a protective layer to prevent chemical degeneration of the core to maintain semiconductor characteristics and/or as a charging layer to impart electrophoretic characteristics to the quantum dot. The shell may be a single layer or a multi-layer. The interface between the core and the shell may have a concentration gradient that decreases toward the center of the element present in the shell.

Examples of the shell of the quantum dot may be an oxide of a metal, a metalloid, or a non-metal, a semiconductor compound, and any combination thereof. Examples of the oxide of a metal, a metalloid, or a non-metal are a binary compound, such as SiO, AlO, TiO, ZnO, MnO, MnO, MnO, CuO, FeO, FeO, FeO, CoO, CoO, or NiO; a ternary compound, such as MgAlO, CoFeO, NiFeO, or CoMnO; and any combination thereof. Examples of the semiconductor compound are, as described herein, semiconductor compounds of Groups II-VI; semiconductor compounds of Groups III-V; semiconductor compounds of Groups III-VI; semiconductor compounds of Groups I, III, and VI; semiconductor compounds of Groups IV-VI; and any combination thereof. In addition, the semiconductor compound may include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AlAs, AlP, AlSb, or any combination thereof. In one or more embodiments, the quantum dot may include InP, GaP, InGaP, ZnSe, ZnS, ZnSeTe, or any combination thereof.

The full width at half maximum (FWHM) of an emission wavelength spectrum of the quantum dot may be about 45 nm or less, for example, about 40 nm or less, for example, about 30 nm or less, and within these ranges, color purity or color gamut may be increased. In addition, since the light emitted through the quantum dot is emitted in all directions, the wide viewing angle can be improved.

In addition, the quantum dot may be a generally spherical particle, a generally pyramidal particle, a generally multi-armed particle, a generally cubic nanoparticle, a generally nanotube-shaped particle, a generally nanowire-shaped particle, a generally nanofiber-shaped particle, or a generally nanoplate-shaped particle. Because the energy band gap can be adjusted by controlling the size of the quantum dot, light having various wavelength bands can be obtained from the quantum dot emission layer. Therefore, by using quantum dots of different sizes, a light-emitting device that emits light of various wavelengths may be implemented. In one or more embodiments, the size of the quantum dot may be selected to emit red, green and/or blue light. In addition, the size of the quantum dot may be configured to emit white light by combining light of various colors. For example, the diameter of the metal oxide may be less than about 20 nm. For example, the diameter of the metal oxide may be from about 0.1 nm to about 20 nm. For example, the diameter of the metal oxide may be from about 1 nm to about 20 nm.

In one or more embodiments, the metal oxide may be an alkali metal oxide, an alkaline earth metal-containing oxide, a rare earth metal-containing oxide, a transition metal oxide, or a combination thereof. In one or more embodiments, the metal oxide may be beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), iron (Fe), zinc (Zn), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), copper (Cu), or any combination thereof. For example, the metal oxide may be ZnO, TiO, WO, MoO, or a combination thereof.

Light-Emitting Device

A light-emitting device according to another aspect includes: a first electrode; a second electrode opposite the first electrode; and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, and at least one of the interlayer may be formed using the nanoparticle ink composition.

Description of

shows a schematic cross-sectional view of an embodiment of a light-emitting device.

The light-emitting deviceincludes a first electrode, an interlayerand a second electrode, and the interlayerincludes an emission layer.

In one or more embodiments, the emission layermay be formed using the nanoparticle ink composition. In this regard, the nanoparticle ink composition may include quantum dots. The quantum dot may be the same as described above. In one or more embodiments, the interlayermay further include a hole-transporting regionbetween the first electrodeand the emission layerand an electron-transporting regionbetween the emission layerand the second electrode.

In one or more embodiments, the hole-transporting regionmay include a hole injection layer (HIL), a hole-transporting layer (HTL), an emission auxiliary layer, an electron-blocking layer (EBL), or any combination thereof. The electron-transporting regionmay include a buffer layer, a hole-blocking layer, an electron control layer, an electron transport layer, an electron injection layer, or any combination thereof. At least one layer of the layers included in the hole-transporting regionand the electron-transporting regionmay be formed using the nanoparticle ink composition. In this regard, the nanoparticle ink composition may include a metal oxide. Description of the metal oxide may be the same as described above. Hereinafter, the structure of the light-emitting deviceaccording to an embodiment and a method of manufacturing the light-emitting devicewill be described in connection with.